1. Field of the Invention
The present invention relates to a walk-behind power tool, such as a lawn mower, snow blower, power sweeper or like equipment, and particularly to a self-propelled walk-behind power tool. More particularly, this invention is directed to a safety cut-off system for preventing the running of a motor under certain conditions when the power tool is left unattended. Furthermore, the instant invention is more particularly directed to a system of presence levers indicating the presence of an operator, for controlling the safety cut-off system.
2. Description of the Related Art
Although the present invention has utility in walk behind snow blowers, power sweepers or the like, the most common utilization of the invention is anticipated for walk-behind type, lawn mowing equipment and particularly in self-propelled, large capacity mowers of the commercial type. Consequently, except where otherwise expressly stated, the description herein is directed to walk behind lawn mowing equipment and particularly commercial type lawn mowers.
Commercial type, self-propelled, walk-behind lawn mowers, commonly have a power deck containing two drive wheels and handle bars for supporting the operating handles or the various mower control elements. The mower, or tool deck, which connects with the power deck, carries idler (or caster) wheels to support and balance the mower deck.
In most cases, such mower decks are detachable with respect to the power deck. As stated above, snow blowers, power sweepers and the like may be used with this power deck. Our description will refer specifically to the lawn mower deck to be used with the power deck, but the explanation applies also to a snow blower, power sweeper or other auxiliary unit. Specifically, because the mower deck is detachable from the power deck, a power take-off unit is provided to transmit power from the power deck to the mower deck. Thus, the motor, on the power deck, provides power to drive the drive wheels, as well as power to drive the auxiliary unit, or the mower deck itself. While many types of power take-off units may be used to transmit power from the power deck to the mower deck, for the purposes of this description, a drive belt will be described, for transferring power from the power deck to the mower deck. Furthermore, a power take-off lever is provided on the handle bar for engaging and disengaging the power take-off unit. Additionally, presence (or dead man) levers are provided on the handle bars.
Mower safety has increasingly been an important factor in the design and development of todays lawn mowers. A current ANSI requirement for a mower with a power take-off (PTO) unit, is that the engine must be cut-off when the machine is unattended. In order to provide for this, mowers in the past have used a presence lever. When the operator is using the mower, the presence lever is grasped along with the handle of the handle bar. When the operator leaves the mower, if the motor and power take-off are both engaged, when the presence lever is released, as the operator walks away, the engine is cut-off.
A problem that occurs in prior art devices is that, often the same presence lever is used for forward and reverse. In some cases, it may create an awkward control situation in which the presence lever must be grasped the same way to pull the mower backwards as to push the mower forward.